Mercury removal systems are designed to remove only particulate waste (amalgam separators), or both particulate and dissolved waste from the dental waste-water slurry using a combination of gravity sedimentation, filtration, chemical oxidation, and ion-exchange materials.
Previously dental waste-water systems, such as those described in U.S. Pat. No. 3,138,873 to Bishop; U.S. Pat. No. 3,777,403 to Ritchie; U.S. Pat. No. 4,385,891 to Ligotti; U.S. Pat. No. 5,205,743 to Ludvigsson et al, were designed to remove dental waste, particularly amalgam. These systems make use of the suction stream to pass the slurry through filters. In these systems the mixture of liquid and solids pass and the solids settle and are removed by a combination of gravity sedimentation and filtration. The dental waste system disclosed in U.S. Pat. No. 5,795,159 to Ralls et al. is differentiated over previously disclosed systems by also incorporating different containers through which the mixture of liquid and solids pass, and solids settle and are removed utilizing the force of gravity and filtration. Most high efficiency waste-water removal systems are designed as centrally located systems, such as disclosed in U.S. Pat. No. 5,885,076 to Ralls, et al and U.S. Pat. No. 6,521,131 to Hamilton, et al. In addition to gravity sedimentation and filtration, these systems utilize a combination of chemical oxidation, precipitation, and/or ion-exchange materials through which the slurry is passed.
Centrally located systems suffer from a number of disadvantages including: 1) location of the apparatus at a distance from the source (i.e. the dental chair), which allows amalgam and mercury to settle and accumulate in dental office plumbing lines, eventually rendering these lines a hazardous waste material in themselves; 2) a requirement to accurately size the system relative to the number of dental chairs serviced, total waste-water accumulation and amount of amalgam waste produced per unit of time; 3) a relatively high level of complexity of installation; 4) an accumulation over time of amalgam waste sludge in settling tanks in addition to the collection within the filters; and 5) the complexity of chemical interactions that can occur over time, especially within holding tanks, between various materials, disinfectants, and chemicals used in the practice of dentistry (and contained within the waste-water slurry), and bacteria and waste materials that accumulate in settling tanks in constant contact with the waste-water slurry containing same. Interaction with various compounds in the holding tanks can result in significant environmental concerns due to chemical interactions or by bacterial conversion of inorganic elemental mercury to organic methyl mercury.
Therefore, despite the often efficient removal of dental waste by centrally located systems, the result can lead to the undertaking of costly hazardous material removal and storage procedures. The associated costs associated with handling and storage of relatively large volumes of material are often beyond the scope of ability of typical dental offices or even dental centers. These costs are further compounded by a the generation of multiple kinds of hazardous waste containers, each of which must be handled separately and using different means. These include: 1) particulate waste removed from the chair side amalgam trap, that are not part of the collection devices; 2) waste accumulated in dental office plumbing lines, which effectively become sedimentation collection lines, and which then represent a permanent residual source of mercury dissolution into the waste stream; 3) sedimentation (holding) tanks designed to collect settled particulate dental sludge; and 4) each of any number of various filters to remove successively finer particles and/or dissolved mercury from the dental waste-water effluent.
A filter apparatus disclosed in U.S. Pat. No. 5,630,939 to Bulard and Gillespie describes an in-line filter assembly capable of trapping tissue and other non-soluable matter during surgical operations. The device can be placed anywhere in the vacuum line. A feature of the apparatus is the ability to disconnect the line and remove the filter, along with trapped matter. However, in order for the filter to be replaced or cleaned, the vacuum must be broken and concomitantly service to the surgical patient. Therefore a need exists for a chairside filter device where filters can be replace on a routine basis without disruption of dental operations.